Data from laboratory animals and primates suggest that environmental contaminants such as dioxin might be associated with the etiology of endometriosis. The extent to which these findings might be relevant for human females remains elusive and served as the impetus for study. The purpose of this exploratory study is twofold: 1) to identify polychlorinated biphenyls (PCB) congeners and pesticides that discriminate women with and without endometriosis and (2) to determine which, if any, of these environmental contaminants predict risk of endometriosis (RO1ES0904501). The study sample comprises 84 women undergoing laparoscopy or laparotomy for diagnosis and/or treatment of endometriosis. Thirty-two women had endometriosis laparoscopically visualized at the time of surgery while 52 did not. In-person interviews were conducted with all women in advance of surgery. Among consenting women (n=80), blood specimens were obtained for the toxicologic analysis of 64 PCB congeners and 7 pesticides. Omentum fat was obtained from the first 15 women enrolled in the study for the analysis of PCBs and pesticides, given the lipophilic properties of these agents. Toxicological analyses were conducted using gas chromatography with electronic data capture. Data analyses are currently underway.